I think it's important to know what problem the no-unused-imports error is solving. See Rob Pike's talk from 2012, and in particular, the section of dependencies in C++: https://talks.golang.org/2012/splash.article#TOC_5.
Basically, the point of no-unused-imports is to reduce compilation time at scale. In the C++ ecosystem, there are lots of redundant and unused #includes. This means that a lot of the bytes sent to the C++ compiler are just thrown away. If you can guarantee that the compiler will never need to look at a source file it does not need to, you can cut down on the compilation time. For small projects, this doesn't matter much. For large projects, it does. Go was designed for large projects.
Basically, the point of no-unused-imports is to reduce compilation time at scale. In the C++ ecosystem, there are lots of redundant and unused #includes. This means that a lot of the bytes sent to the C++ compiler are just thrown away. If you can guarantee that the compiler will never need to look at a source file it does not need to, you can cut down on the compilation time. For small projects, this doesn't matter much. For large projects, it does. Go was designed for large projects.