Laravel 5.2：Auth :: attempt（）不起作用

Tonight I tried Auth::attempt in Laravel 5.2. I already read some case but, it's not solve my problem at all.

This is my doLogin function:

public function doLogin(LoginRequest $request)
{   
    $customer = [
        'email' => $request->input('email'),
        'password' => $request->input('password') 
    ];
    if (Customer::where('email', '=', $request->input('email'))->exists()) {
        if (Auth::attempt($customer)) { 
            print_r(Auth::user());exit();
        } else {
            return response()->json([
                'error' => true,
                'status_code' => 400,
                'message' => 'Wrong Credential, Please check your email or password'
            ]);     
        }
    } else {
        return response()->json([
            'error' => true,
            'status_code' => 404,
            'message' => 'email not found'
        ]);
    }    
}

I'm already hashing the password stored in database using bcrypt() and I have the password field in my database.

Also, I already changed the $primaryKey = 'customer_id';

But the result always returns false (wrong credentials), did I wrote something wrong?