Wow! You are right! Running go build on host instead of container is 1.16 times faster! A whopping 435ms difference! Amazing!

    /tmp/gitea $ hyperfine -p 'go clean -cache' 'make backend' 'docker run --rm -v $PWD:/build -v $HOME/.go:/go -w /build golang:1.22.3 make backend'
    Benchmark #1: make backend
      Time (mean ± σ):      2.766 s ±  0.021 s    [User: 8.429 s, System: 1.590 s]
      Range (min … max):    2.732 s …  2.800 s    10 runs

    Benchmark #2: docker run --rm -v $PWD:/build -v $HOME/.go:/go -w /build golang:1.22.3 make backend
      Time (mean ± σ):      3.201 s ±  0.034 s    [User: 9.9 ms, System: 7.7 ms]
      Range (min … max):    3.135 s …  3.235 s    10 runs

    Summary
      'make backend' ran
        1.16 ± 0.01 times faster than 'docker run --rm -v $PWD:/build -v $HOME/.go:/go -w /build golang:1.22.3 make backend'

(For incremental build, tested with `hyperfine --warmup 1 'make backend' 'docker run --rm -v $PWD:/build -v $HOME/.go:/go -v $HOME/.cache/go-build:/root/.cache/go-build -w /build golang:1.22.3 make backend'` it's 812.9 ms vs 1.146s.)