Pin futures to 0.3.0-alpha.18

Author: skade

Cargo.toml

@@ -50,9 +50,9 @@ surf = "1.0.2"
 tempdir = "0.3.7"
 
 # These are used by the book for examples
-futures-channel-preview = "0.3.0-alpha.18"
-futures-util-preview = "0.3.0-alpha.18"
+futures-channel-preview = "=0.3.0-alpha.18"
+futures-util-preview = "=0.3.0-alpha.18"
 
 [dev-dependencies.futures-preview]
-version = "0.3.0-alpha.18"
+version = "=0.3.0-alpha.18"
 features = ["std", "nightly", "async-await"]