How to mock grpc in Go unit test

I have the following code in Go:

func (s UserServer) getUser(user string) (*User, error) {
    conn, err := grpc.DialContext(ctx, s.userSvcAddr,
        grpc.WithInsecure(),
        grpc.WithStatsHandler(&ClientHandler{}))
    if err != nil {
        return nil, fmt.Errorf("could not get the user: %+v", err)
    }
    defer conn.Close()

    user, err := s.NewUser(conn)
    return user, nil
}

How to mock the grpc.DialContext in the unit test?