Drop support for go1.18 and go1.19

Author: nekohasekai

.github/workflows/debug.yml

@@ -37,38 +37,6 @@ jobs:
       - name: Build
         run: |
           make test
-  build_go118:
-    name: Linux Debug build (Go 1.18)
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-      - name: Setup Go
-        uses: actions/setup-go@v4
-        with:
-          go-version: ~1.18
-        continue-on-error: true
-      - name: Build
-        run: |
-          make test
-  build_go119:
-    name: Linux Debug build (Go 1.19)
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-      - name: Setup Go
-        uses: actions/setup-go@v4
-        with:
-          go-version: ~1.19
-        continue-on-error: true
-      - name: Build
-        run: |
-          make test
   build_go120:
     name: Linux Debug build (Go 1.20)
     runs-on: ubuntu-latest

go.mod

@@ -1,6 +1,6 @@
 module github.com/sagernet/sing
 
-go 1.18
+go 1.20
 
 require (
 	github.com/stretchr/testify v1.9.0