Update for async-graphql v2.0.0

Author: sunli829

Cargo.lock

@@ -5,8 +5,9 @@ authors = ["sunli <[email protected]>"]
 edition = "2018"
 
 [dependencies]
-async-graphql = { version = "2.0.0-alpha.7" }
+async-graphql = { version = "2.0.0" }
 async-std = { version = "1.5.0", features = ["attributes"] }
-juniper = { git = "https://github.com/graphql-rust/juniper", rev = "8b79f5b"}
+juniper = { git = "https://github.com/graphql-rust/juniper", rev = "68210f5"}
 futures = "0.3.4"
 serde_json = "1.0"
+lazy_static = "1.1.1"