feat: check unused package (#232)

* feat: check unused package

update edganiukov/fcm to appleboy/go-fcm

* update readme

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* update comment

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

vendor/github.com/appleboy/go-fcm/option.go

@@ -0,0 +1,28 @@
+package fcm
+
+import (
+	"errors"
+	"net/http"
+)
+
+// Option configurates Client with defined option.
+type Option func(*Client) error
+
+// WithEndpoint returns Option to configure FCM Endpoint.
+func WithEndpoint(endpoint string) Option {
+	return func(c *Client) error {
+		if endpoint == "" {
+			return errors.New("invalid endpoint")
+		}
+		c.endpoint = endpoint
+		return nil
+	}
+}
+
+// WithHTTPClient returns Option to configure HTTP Client.
+func WithHTTPClient(httpClient *http.Client) Option {
+	return func(c *Client) error {
+		c.client = httpClient
+		return nil
+	}
+}