Fix small typo in README.md
@@ -13,7 +13,7 @@ go get github.com/faiface/pixel
If you are using Modules (Go 1.11 or higher) and want a mutable copy of the source code:
```
-git clone https://github.com/faiface/pixel ;# clone outside of GOPATH
+git clone https://github.com/faiface/pixel # clone outside of $GOPATH
cd pixel
go install ./...
```
