Implementation contracts in Go

Tit Petric — Tue, 09 Jun 2026 18:00:00 +0200

For a long time, I considered a filled interface type as an implementation contract in Go. A very quick shorthand on how you can check for implementation compliance is to add the following snippet to your _test.go files:

        
var _ rpc.UserService = &UserService{}

Until your UserService meets the interface contract, the test will result in failure. You’re likely to add this check to ensure your API is decoupled and can be used behind that interface.

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Implementation contracts in Go