这个golang代码有什么作用？ [重复]

Question

This question already has an answer here:

• What does an underscore and interface name after keyword var mean? 2 answers

I was reading DigitalOcean's golang client. I noticed that they create an instance of their *Op struct in a _ variable. Example: https://github.com/digitalocean/godo/blob/master/droplets.go#L32

var _ DropletsService = &DropletsServiceOp{}

Why is this line needed?

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Answer 1

This line is a compile time check that *DropletsServiceOp satisfies the DropletsService interface.

The line has no effect on the execution of the program.