The main Go program I work on is CloudFlare's Railgun which is 18,000 lines of code. It builds in 4s.

   % make clean
   % time make make-listener make-sender make-diag make-ssl...
   3.42s user
   1.05s system
   105% cpu
   4.240 total
   % find src/ -name '*.go' | xargs wc -l | tail -1
   17870 total

And that's building everything sequentially. If I switch to using -j4 I get a 2s build from clean.

   % make clean
   % time make -j4 make-listener make-sender make-diag make-ssl...
   5.75s user
   1.99s system
   382% cpu
   2.020 total

An incremental build (no op) of the entire tree is one second:

   % time make -j4 make-listener make-sender make-diag make-ssl...
   1.56s user
   0.73s system
   209% cpu
   1.090 total

Yes, we wrap the go build tools with make. Not because they are lacking anything for Go but because we do other stuff (like build documentation and release packages).

(I should have not counted the tests in the above analysis. There are 7,290 lines of tests and 10,580 lines of code).