alter env syntax, move expansion to commands

.drone.yml

@@ -7,12 +7,12 @@ pipeline:
     mem_limit: 3G
     image: therecipe/qt:linux
     environment:
-      QT_DIR: /opt/Qt
-      QT_DOCKER: 'true'
-      QT_API: 5.12.0
-      GOPATH: /home/user/work:/media/sf_GOPATH1/
-      PATH: $PATH:/home/user/work/bin:/media/sf_GOPATH1/bin
+      - QT_DIR=/opt/Qt
+      - QT_DOCKER='true'
+      - QT_API=5.12.0
+      - GOPATH=/home/user/work:/media/sf_GOPATH1/
     commands:
+      - export PATH=$PATH:/home/user/work/bin:/media/sf_GOPATH1/bin
       - echo $PATH
       - apt-get -qq update && apt-get --no-install-recommends -qq -y install ca-certificates curl git
       - go get