User form is the tool that is commonly used when we develop web applications, it provides ability to communicate between clients and servers. You must know form very much if you are web developers; if you are C/C++ programmers, you may want to ask: what is the user form?
Form is the area that contains form elements. Users can input information in these elements, like text box, drop down list, radio buttons, check box, etc. We use form tag <form> to define form.
<form>
...
input elements
...
</form>
Go has already had many convenient functions to deal with use form, like you can easily get form data in HTTP requests, and there are easy to integrate to your own web applications. In section 4.1, we are going to talk about how to handle form data in Go, and because you cannot believe any data from clients, you have to verify data before use them. After that, we will show some examples about verifying form data in section 4.2.
We say that HTTP is stateless, how can we identify that these forms are from same user? And how to make sure that one form can only be submitted once? We have more detailed explanation about Cookie (Cookie is the information that can be saved in the client side, and put in the request header when the request is sent to the server) in both sections 4.3 and 4.4.
Another big feature of form is uploading files. In section 4.5, you will learn how to use this feature and control file size before it starts uploading in Go.
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