Related #27921

What happens if you write a C file

#include <stdlib.h>
#include <stdio.h>

int main() { printf("Hello, world\n"); return 0; }

and try to compile that using cc main.c?

If you get the same error about stdlib.h, then the problem is with your C compiler installation, not with Go.

Related #27921

Thanks for sharing, one of the comment in that issue works for me:
$ brew unlink llvm@4

What happens if you write a C file

#include <stdlib.h>
#include <stdio.h>

int main() { printf("Hello, world\n"); return 0; }

and try to compile that using cc main.c?

If you get the same error about stdlib.h, then the problem is with your C compiler installation, not with Go.

Thanks for following up, below are my test result:
cc ok
gcc ok
clang: 'stdlib.h' file not found

The problem has been solved after I run: brew unlink llvm@4

From the discuss above and my issue( I installed an older version clang6 pkg and leave an export in my .bash_profile), all these caused by clang. So
FIRST check the environment in terminal with
clang -v
Change to use the Xcode installed clang, for macOS Catalina 10.15.4 is 11 or 12. All will done.