Update README.md

Author: cloudwebrtc

tools/README.md

@@ -2,16 +2,22 @@
 
 This tool is used to demonstrate the basic push process for verifying callkeep. The tool is written in golang.
 
+prepare to run:
+
+`cd tools && go mod tidy`
+
 ## For iOS APNS
 
 please refer to `https://developer.apple.com/account/resources/certificates/add`.
-Choose `VoIP Services Certificate` to create a push certificate, download voip_services.cer and install it to the keychain tool, and export its private key rename it to `callkeep-apns.p12`
+
+Choose `VoIP Services Certificate` to create a push certificate, download `voip_services.cer` and install it to the keychain tool, export its private key rename it to `callkeep-apns.p12`
 
 `go run cmd/main.go -i +8618612345678 -p apns -d $ios_device_token`
 
 ## For Android FCM
 
 please refer to `https://console.firebase.google.com/project/[your project]/settings/serviceaccounts/adminsdk`
-Select the `go` sdk format under your fcm project to download serviceAccountKey.json and rename it to `callkee-fcm.json`
+
+Select the `go` sdk format under your fcm project to download `serviceAccountKey.json` and rename it to `callkee-fcm.json`
 
 `go run cmd/main.go -i +8618612345678 -p fcm -d $android_fcm_token`