Why not? They certainly define contracts for the type - at least that's my non-native speaker understanding of the english word. It might seem weird if one use

Why not? They certainly define contracts for the type - at least that's my non-native speaker understanding of the english word. It might seem weird if one used a different programming language which used the term for a slightly different concept - but that doesn't mean Go's usage is bad. The concept is similar to what concepts are in C++ and traits in Rust. And from those terms I actually find contract to be the most understandable for people who are new to these things.