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How do you set headers in an HTTP response in Go?

To set headers in an HTTP response in Go, you can use the http.ResponseWriter interface's Header() method to get the header map, and then use the Set() method to add or update headers.
Set headers in an HTTP response

Example

func handlerFunc(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)
    fmt.Fprintln(w, `{"message": "Hello, world!"}`)
}

In this example, the Content-Type header is set to application/json, indicating that the response will contain JSON data. The WriteHeader() method is then called to set the HTTP status code to 200 (OK). Finally, the fmt.Fprintln() function is used to write the response body to the http.ResponseWriter object.

Note that headers must be set before writing any data to the response body, as the headers are sent as part of the response's initial HTTP header.

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