Temporary migrate tests from node 11.7 to 11.6 to fix codecov (#1690)
Temporary migrate tests from node 11.7 to 11.6 to fix codecov (#1690)

Fixes #1682
graphql/graphql-js,enaqx/graphql-js,enaqx/graphql-js,graphql/graphql-js,graphql/graphql-js,enaqx/graphql-js