Gotchas

Sun, 04 Oct 2026 00:00:00 +0000

No overloading, no default arguments

One name, one signature. Use an options struct or functional options:

type Option func(*Server)

func WithTimeout(d time.Duration) Option { return func(s *Server) { s.timeout = d } }

func NewServer(addr string, opts ...Option) *Server {
    s := &Server{addr: addr, timeout: 30 * time.Second}
    for _, o := range opts {
        o(s)
    }
    return s
}

srv := NewServer(":8080", WithTimeout(5*time.Second))

A nil pointer in an interface is not a nil interface

func find() error {
    var e *MyError // nil
    return e       // interface holding (*MyError, nil)
}

find() == nil // false (!)

An interface is (type, value); it’s only nil when both are. Return a literal nil on success.

Pitfalls on Notes

Gotchas

No overloading, no default arguments

A nil pointer in an interface is not a nil interface