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So this time around, we want to experiment with and write our first bit of middleware and the first



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middleware we write is going to be completely useless.



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The entire purpose of it is just to show you how middleware works and how you might go about writing



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it.



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So what I want to do is this is my roots file and I want to write some middleware that says every time



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somebody hits a page, just write something to the console.



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So in other words, format, print, line and some kind of message.



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So to make that happen, the very first thing I have to do is create a new file, create a new go file



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in command web called middleware.



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Go.



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All right.



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In the middleware I go, I'm going to create a function and I'm going to create a function that's going



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to look a little bit odd to you at first, but I'll explain it to you.



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So, first of all, let's give it a name func right to console.



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That's my function.



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And it's going to take one parameter and I'm going to call that parameter next, which is pretty common



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to name the parameter in middleware next.



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When you're writing middleware, it's of type HTP Tandler and it returns and htp dot oops, HDB handler



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as well.



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And inside of that I'm going to write a return function.



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I'm going to return a type of htp dot handler func.



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Inside of that I'm going to have an anonymous function func and it's going to take as most things to



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deal with handlers due to arguments w htp dot response writer and our star request, which you've seen



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many times by this point, and that is going to inside of that return function.



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Here's what we're actually returning a better put a capital H there.



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What we're going to return is something that's really simple.



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We're going to say print to the console format, dot print line, hit the page, OK?



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And then we need to at the end of this, we need to move onto the next and the next might be another



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bit of middleware or it might be the part in our file where we actually return our mux.



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So we'll just say next dot serve http w our response writer and the pointer to the request.



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So now I've written this little bit of this little bit of code that's just a bit of middleware and it's



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a function, it has a name, it takes an argument which is a handler, it returns a handler.



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And inside of that I have the return function which consists of an anonymous function cast to a handler



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func, and that that will actually allow us to serve our middleware.



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OK, so how do I use this?



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Well, the same way I used other middleware.



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I'll go back to my roots folder and I will say, are my roots file and say Muxtape use?



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And I called it right to console.



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That's it.



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That's all I should have to do.



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So if I start my application by going to my terminal window and writing Go Run Command Web Stargirl,



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I'm now compiling three files in my web folder, Main Middleware and Roots and run that.



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Good, so it's running and then I go over to my Web browser and I just reload this page a few times,



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so I've reloaded it three times and I come back and there wrote the middleware three times.



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That's how you write basic middleware.



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And most middleware, actually, all middleware will have a very similar format to what you're seeing



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right here now.



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There'll be other instances where you don't have to have this anonymous function and you just return



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on HTP Handler and we'll be seeing that in just a moment.



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Actually, right now, before too much longer, we're going to start building a useful application.



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Right now, our application is nothing.



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It's just showing us how things work.



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We have one about page which really has no information.



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We have one home page that has no information.



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We're actually going to build an application and I'll be talking about that.



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Not the next section.



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The section after that, probably we're going to build an application that we'll actually have forms



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on the page, for example.



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And you may recall a while ago, I said in that default data, let's find that render function right



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here actually is not there.



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And we put it into where is it, template data.



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Remember when we made this model for template data, I said we're going to be using C SRF tokens.



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Well, now is the perfect time to actually look at how we can populate that.



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We're going to do the whole thing, but we'll get started.



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That CSR CSR token stands for cross site request forgery token.



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And it's nothing more that when you build a Web page, you have a hidden with a form on it.



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You have a hidden field in that form, which is a long string of random numbers, and they change every



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single time somebody goes to a page.



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Well, that seems to me like a really suitable place for middleware instead of as we've done here in



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this right to console, just format, print line, hit the page.



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We could generate that token.



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Well, it turns out there's a really good package which already exists that does precisely that.



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Let's go to Google and find Googling.



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No search because it's called no surf.



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I put any on there.



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Let's get rid of that.



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Here it is, GitHub.



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So this is a vulnerability, but that gives me the name of it, that's all I really want.



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So let's copy that paste into here.



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And this is a nice little package that actually generates this for us.



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It's an easy package for go that helps you prevent CSF.



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So how do we actually use this?



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It's pretty straightforward.



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Let's find our install package.



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We shouldn't bother giving it to me, but I can figure it out or copy that part of the URL.



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Go back to my terminal or my I.D. Stop the application and clear the screen.



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Go get that.



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So it's gone and gotten it for us.



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Let's make sure it's in our goman because I like to verify those sort of things.



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Go on.



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There it is, it's installed.



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Well, we can actually use this without too much difficulty at all.



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So back in my middleware, well, first of all, my roots, let's get rid of this one.



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We're not actually going to do anything with because it's useless.



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Delete that back in here.



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I'll delete this because I'm not using it.



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Actually, only that there is a reference.



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It's not hurting anything because it's never called.



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I need to create a new bit of middleware func no serve next htp dot handler and it returns and htp dot



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handler as all middleware must.



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And what I'm going to do here is create a new variable, CSIR, F Tandler.



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I can call it whatever I want, but that's a meaningful name equals no sirf dot.



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Knew, and then I put in my next variable, so I'm taking this handler, which is an argument to I think



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I misspelled that.



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No, sir.



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There we are.



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And I'm taking the argument that this an HP handler passed to this Nosseir function, I'm using that



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as an argument to know Cerf knew, which will actually create a handler for us.



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And then I need to set some values for this.



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See SRF Handler.



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We need to set the base cookie because it uses cookies to make sure that the token it generates is available



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on a per page basis.



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So inside of that, we have the argument htp cookie, we're creating a new cookie and that's going to



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be HTP only, let's you say true for that path, cookie path.



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I want this to apply to the entire site.



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So Slash is the way that you refer to the entire site for a cookie secure?



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I'm going to say false because we're not running on HTP right now, but in production will actually



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change that to true and same site.



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The fourth parameter, we'll just use the in standard for that, which is same site, lax mode.



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All right.



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That's just enough information to create our No.



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SIRF token.



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That's all that we need.



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So we've installed the package.



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No SIRF now we've created new middleware for no surf and we need of course to use it.



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We have one error here somewhere.



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What is that error.



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Oh yeah.



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I got to return something.



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I better return CSIR handler there because if I don't return something we're never going to get past



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this bit of middleware.



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Let's go back to our Roots folder and now so we want to use my best use and I called it nurser.



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That's it.



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So now this should still compile, let's compile it, go run, command, web, go.



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It does perfect.



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And I should be able to reload the pages here.



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No problem at all, it does exactly what I want.



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So we've now put in a bit of middleware, which we're going to use a little bit later in the course



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when we start process are building forms and processing form posts.



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But that's really all you need to worry about for making middleware.



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And as time goes on, we'll be adding to this and we might even be using some more external packages.



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But this gives us a good start.



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All right.



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We need to move on next to sessions, which will also require us to use some middleware.



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That's enough for this time around.