How to get rid of the warning?

Question

go

I'm trying to write a jwt middleware that will pass data from the token to the next function via context.

ctx := r.Context()
ctx = context.WithValue(ctx, "userID", tk.UserID)
ctx = context.WithValue(ctx, "token", tk.Token)

next.ServeHTTP(w, r.WithContext(ctx))

But such a code is underlined in yellow and a message is displayed. What am I doing wrong?

should not use basic type string as key in context.WithValue

Answer 1

You cannot use strings as keys, this will sooner or later lead to name conflicts.
When checking a key for a match, the context library compares the value and type of the key.
The key must not be a simple type, such as string, int, etc.
You need to create a separate type for the key.
This approach will allow you to have several values ​​in the context with the same key, but of a different type.
Here is an example of how to do it right:

type contextKey uint

const (
    UserIDContextKey contextKey = 1
)
...
ctx := r.Context()
ctx = context.WithValue(ctx, UserIDContextKey, tk.UserID)