Use same headers for every request - http

Question

I want to be able to use the same headers for every request made by an HTTP client without having to specify them for every request like so:
req, err := http.NewRequest("GET", fmt.Sprintf("https://%s", endpoint), nil)
if err != nil {
log.Printf("Error making request to endpoint: %+v", err)
return p, err
}
req.Header.Add("Authorization", "Bearer")
req.Header.Add("Version", "2017-11-23")
resp, err := client.Do(req)
Is there a way to configure this on the client?

Answer 1

Use a function to encapsulate the code to create and configure the request:
func newRequest(endpoint string) (*http.Request, error) {
req, err := http.NewRequest("GET", fmt.Sprintf("https://%s", endpoint), nil)
if err != nil {
return nil, err
}
req.Header.Add("Authorization", "Bearer")
req.Header.Add("Version", "2017-11-23")
return req, nil
}
A more complicated approach is to implement a round tripper that adds the headers and delegates to another round tripper:
type transport struct {
underlyingTransport http.RoundTripper
}
func (t *transport) RoundTrip(req *http.Request) (*http.Response, error) {
req.Header.Add("Authorization", "Bearer")
req.Header.Add("Version", "2017-11-23")
return t.underlyingTransport.RoundTrip(req)
}
Use it to create a client like this:
c := http.Client{Transport: &transport{ underlyingTransport: http.DefaultTransport } }
The transport adds the headers on calls to c.Do(), c.Get(), c.Post(), etc.