[chore] Update Go version to 1.18 (#444)

* linting with new golangci-lint version

* update go to 1.18

* bump versions in drone.yml

* use new runtime/debug package for version info

* remove Commit build flag from goreleaser

* remove mock commit + version from build script

* go fmt

* add dummy version env flag to test container

* install git in golang container for testing

* only set versionString if Version is defined

internal/cache/account.go

@@ -91,7 +91,13 @@ func (c *AccountCache) getByID(id string) (*gtsmodel.Account, bool) {
 	if !ok {
 		return nil, false
 	}
-	return copyAccount(v.(*gtsmodel.Account)), true
+
+	a, ok := v.(*gtsmodel.Account)
+	if !ok {
+		panic("account cache entry was not an account")
+	}
+
+	return copyAccount(a), true
 }
 
 // Put places a account in the cache, ensuring that the object place is a copy for thread-safety