Upgrade to go@1.12.7

Author: tanx

.travis.yml

@@ -15,7 +15,7 @@ env:
   global:
     - LND_TAG=add905d17f7bbb11d0df2761cdf8accf2fef2b00
     - BTCD_TAG=16327141da8ce4b46b5bac57ba01352943465d9e
-    - GO_TAG=1.12.1
+    - GO_TAG=1.12.7
     - GOROOT=$HOME/go
     - GOPATH=$HOME/gocode
     - PATH=$GOPATH/bin:$GOROOT/bin:$PATH