How do I Pass Context in Golang Requests to Middleware and Handlers?

How to Pass Context in Golang Requests to Middleware

In Golang, the concept of context allows developers to pass data and modify requests within handlers and middleware. To effectively use context, it's crucial to understand how to pass it correctly.

When defining a middleware, it's necessary to wrap the provided handler to incorporate additional functionality. This is achieved using a Closure, which returns an HTTP handler with the desired modifications. The context can then be passed to the underlying handler by calling its ServeHTTP() method.

For instance, to authenticate users, you could create a middleware function called checkAuth(), which receives an authentication token and returns another function. This function wraps the actual handler that handles the request and checks if the request contains a valid token.

Next, consider the Handler struct, which represents the handler responsible for processing requests. Inside its ServeHTTP() method, the handler may need to access information from the context, such as decoding request parameters or passing data to external services.

In the main function, you initialize the router and call mux.NewRouter() to create a new instance. To pass the context to the authorized middleware, you derive the context from the Background context by using the WithContext() method on the request.

Finally, to access the passed context within the middleware, you can retrieve it by calling r.Context(). You can then store additional information in the context using the WithValue() method and retrieve it later in the handler.

By following these steps, you can effectively pass context in Golang requests to middleware and to the handler, enabling the modification of requests and the sharing of data across different parts of your application.

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