How to prevent background jobs from printing next to prompt?

Question

I am trying to implement my own shell and am experimenting with background jobs with using WNOHANG option in waitpid. But whenever I run a command in shell it just prints the output next to my prompt like this:

user@hostmachine:/.../$: [output]

Where am I going wrong? `

    while (1) {
      int childPid, status;

      // Display prompt and read input
      char *buffer = print_prompt();
      char *input = readline(buffer);
      check_and_free(buffer)

//    add input to readline history.
      add_history(input);
      time_t t;
      time(&t);
      add_history_time(ctime(&t));

      // Check for EOF.
      if (!input)
         break;

      parseInfo *result = parse(input);
      if (result == NULL) {
         goto free;
      }
      print_info(result);

      commandType *input_command = &result->CommArray[0];

//    execute builtin command in parent process
      int commType = isBuiltInCommand(input_command->command);
      if (commType == EXIT) {
         free_info(result);
         check_and_free(input)
         exit(0);
      }
      else if (commType != NO_SUCH_BUILTIN) {
         executeBuiltInCommand(input_command, commType, history_get_history_state());
      } else {
//       create a child process to execute command
         childPid = fork();
         if (childPid == 0) {
//          calls execvp
            printf("Executing child process...\n\n");
            executeCommand(input_command, result);
         } else {
            waitpid(childPid, &status, WNOHANG);
            if (status != 0) {
               printf("Error! Child exited with error code %d\n", WEXITSTATUS(status));
            }
         }
      }
      // Free buffer that was allocated by readline
      free:
      free_info(result);
      check_and_free(input)
   }
   return 0;
}

`

I tried to execute a job in background and for quick ones like "ls" it just prints the output next to my prompt!