https://github.com/golang/go/issues/15538

cbin.c

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <dlfcn.h>
#include <errno.h>

typedef void (*golib_func)(void);

int main() {
	void			*golib = NULL;
	golib_func 		f;
	pid_t           child = -1;

	// load lib and func symbol
	if (NULL != (golib = dlopen("golib.dylib", RTLD_NOW))) {
		if (NULL != (f = dlsym(golib, "TestNetDial"))) {
			printf("Calling from parent:\n");
 			(*f)();

 			// fork
 			if (0 < (child = fork())) {
				waitpid(child, NULL, 0);
				dlclose(golib);
 			} else if (0 == child) {
				// call golib from child pid
				printf("Calling from child:\n");
 				(*f)();
				exit(0);
 			} else {
				printf("failed fork: 0x%0X\n", errno);
			}
		} else {
			printf("%s\n", dlerror());
		}
	} else {
		printf("%s\n", dlerror());
	}
}

golib.go

package main

import "C"

import (
	"fmt"
	"net"
)

func main() {
	// nothing to do here
}

//export TestNetDial
func TestNetDial() {
	conn, err := net.Dial("tcp", "golang.org:443")
	if err != nil {
		panic(err)
	}

	defer conn.Close()

	fmt.Printf("--> Connected to %s\n", conn.RemoteAddr())
}

Makefile

all: cbin golib.dylib

cbin: cbin.c
	gcc -o cbin cbin.c

golib.dylib: golib.go
	go build -buildmode=c-shared -o golib.dylib golib.go

clean:
	rm -vf cbin golib.dylib

.PHONY: all clean

FYI Makefile targets OS X. replace s/dylib/so/g for Linux.