Go interfaces are implicit: a type satisfies an interface by having the right…

Sun, 19 Jul 2026 12:00:00 +0000

Go interfaces are implicit: a type satisfies an interface by having the right methods, no implements keyword.

Closest Python equivalent is typing.Protocol (structural subtyping, checked by mypy), but Go enforces it at compile time, not via a separate type checker.
Sharp edge: a nil concrete pointer wrapped in an interface value is not nil. var dog *Dog = nil; var s Speaker = dog gives s != nil because the interface holds (*Dog, nil), a typed pair. Bites hardest when returning error interfaces.
Go proverb: “the bigger the interface, the weaker the abstraction.” Keep them to 1-3 methods, define where consumed not where implemented.

golang on Saurabh Kumar