(build) use only the latest LTS - 3.1

Author: arturcic

.github/workflows/build.yml

@@ -103,7 +103,7 @@ jobs:
     strategy:
       matrix:
         os: [linux]
-        targetFramework: [2.1, 3.1]
+        targetFramework: [3.1]
         distro: [alpine.3.10-x64, centos.7-x64, debian.9-x64, fedora.30-x64, ubuntu.16.04-x64, ubuntu.18.04-x64]
       fail-fast: false
 
@@ -233,7 +233,7 @@ jobs:
     strategy:
       matrix:
         os: [linux]
-        targetFramework: [2.1, 3.1]
+        targetFramework: [3.1]
         distro: [alpine.3.10-x64, centos.7-x64, debian.9-x64, fedora.30-x64, ubuntu.16.04-x64, ubuntu.18.04-x64]
       fail-fast: false
 

src/Docker/docker.json

@@ -1,13 +1,5 @@
 {
     "linux": {
-        "2.1": [
-            "alpine.3.10-x64",
-            "centos.7-x64",
-            "debian.9-x64",
-            "fedora.30-x64",
-            "ubuntu.16.04-x64",
-            "ubuntu.18.04-x64"
-        ],
         "3.1": [
             "alpine.3.10-x64",
             "centos.7-x64",
@@ -18,9 +10,6 @@
         ]
     },
     "windows": {
-        "2.1": [
-            "nanoserver"
-        ],
         "3.1": [
             "nanoserver"
         ]