Writing to C program using GO but C program doesn't stop at scanf()

Question

In these snippets the go program tries to write to C program's stdin. The problem is that the c program starts an infinite loop after the go loop finishes.

main.c

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


int main(){
    int age;
    char name[8]; 

    for(;;)
    {
    scanf(" %s : %d\n",&name, &age);
    printf("%s : %d\n",name, age);
    }
    return 0;
}

run/main.go

func main() {

    proc := exec.Command("../main")
    stdin, err := proc.StdinPipe()
    if err != nil {
        fmt.Println(err) 
    }

    defer stdin.Close()

    proc.Stdout = os.Stdout
    proc.Stderr = os.Stderr

    fmt.Println("START")                      
    if err = proc.Start(); err != nil { 
        log.Fatal("An error occured: ", err)
    }

    for i := 0; i < 500; i++ {
        io.WriteString(stdin, fmt.Sprintf("hello : %d\n", i))
        //How to wait here and read from printf()?
    }

    //proc.Process.Kill() Here proc gets killed too fast

    fmt.Println("END")
}

When killed, process doesn't complete it's output

Output

START
END
hello : 497
hello : 498
hello : 499
hello : 499 

Output Expected

START
....
hello : 497
hello : 498
hello : 499
END