具体表现

$ go build
# golang.org/x/sys/unix
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/syscall_darwin.1_13.go:25:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.1_13.go:27:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.1_13.go:40:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:28:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:43:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:59:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:75:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:90:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:105:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:121:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.go:121:3: too many errors

解决方法

$ go get -u golang.org/x/sys