Bring Swift to 5.2.1 in Github Actions (#123)

Author: gliptak

.github/workflows/SwiftPlot_Ubuntu.yml

@@ -5,6 +5,9 @@ on:
     branches: master
   pull_request:
 
+env:
+  SWIFT_VERSION: 5.2.1
+
 jobs:
   build:
 
@@ -17,11 +20,11 @@ jobs:
     - name: Install Swift Dependencies
       run: sudo apt-get install clang libicu-dev
     - name: Download Swift
-      run: wget "https://swift.org/builds/swift-5.1.3-release/ubuntu1804/swift-5.1.3-RELEASE/swift-5.1.3-RELEASE-ubuntu18.04.tar.gz"
+      run: wget "https://swift.org/builds/swift-${{ env.SWIFT_VERSION }}-release/ubuntu1804/swift-${{ env.SWIFT_VERSION }}-RELEASE/swift-${{ env.SWIFT_VERSION }}-RELEASE-ubuntu18.04.tar.gz"
     - name: Install Swift
       run: |
-        tar xzf swift-5.1.3-RELEASE-ubuntu18.04.tar.gz
-        echo "::add-path::$(pwd)/swift-5.1.3-RELEASE-ubuntu18.04/usr/bin"
+        tar xzf swift-${{ env.SWIFT_VERSION }}-RELEASE-ubuntu18.04.tar.gz
+        echo "::add-path::$(pwd)/swift-${{ env.SWIFT_VERSION }}-RELEASE-ubuntu18.04/usr/bin"
     - name: Build
       run: swift build -v
     - name: Run tests