These sorts of symptoms on macOS often indicate a broken Xcode install or some other, incompatible gcc toolchain earlier in $PATH.

In this particular case, it appears that you have an invalid pthread.h: size_t is defined in stddef.h, which pthread.h should #include as needed. Similarly, struct timespec should be provided by time.h (#included here); the fact that it is missing suggests that something is very wrong in your C include path.

Are you able to build C programs in the same environment?

You may be able to run which clang and/or find / -name time.h to locate the bad headers; as a last resort, you could try removing and reinstalling Xcode.

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)

FYI if anyone like me found themselves in this situation, check your /usr/local/include folder for header files *.h.

Delete these and you'll get unstuck. Don't ask me how I got myself into that situation, but I think it was screwing around with brew.

Are you able to build C programs in the same environment?

You may be able to run which clang and/or find / -name time.h to locate the bad headers; as a last resort, you could try removing and reinstalling Xcode.

@bcmills Please help me, I meet this problem too.

I can build C programs in the project, but when I run go test . command, then terimnal will show the message of gcc_libinit.c: 105:14: error: use of undeclared identifier 'EAGAIN😭

@zhulinwei This issue is closed, and at this point there is no reason to think that there is a problem with Go. You will most likely find a better answer on a forum. See https://golang.org/wiki/Questions.

@ianlancetaylor thanks very much, I fix this problem by env CGO_ENABLED=0 go test, but I am not sure if it will cause other problems.

FYI if anyone like me found themselves in this situation, check your /usr/local/include folder for header files *.h.

Delete these and you'll get unstuck. Don't ask me how I got myself into that situation, but I think it was screwing around with brew.

Same. This worked for me. Was afraid of removing to bulk renamed them to .x from .h

I solved this problem, and I hope my answer can help others.

If you don't need to work with c lang, you can export CGO_ENABLED=0,

else you can change your CC, replace clang with gcc, eg export CC=gcc

I know this is older but this solved my problem
go env -w CGO_ENABLED=0
Unclear whether or not it'll cause other problems though.

For what it's worth, we've seen a lot of macOS C issues from folks who have installed Anaconda or Miniconda (see #29597). It might be worth investigating those as the source of corrupted C headers.