Ahmed Magdy

from search_key to key

## Describe the bug Sometimes we get the error 1093 fatal error: concurrent map writes 1095 goroutine 409 [running]: 1096 github.com/gruntwork-io/terragrunt/config.copyFieldsMetadata(...) 1097 /home/circleci/project/config/include.go:835 1098 github.com/gruntwork-io/terragrunt/config.(*TerragruntConfig).Merge(0xc00699a900, 0xc0049cbc20, 0x21137d8?) 1099 /home/circleci/project/config/include.go:297 +0xae8...