ci: remove support for older Go versions in workflows and go.mod

- Remove support for Go versions 1.18, 1.19, and 1.20 from GitHub Actions workflow
- Remove `toolchain go1.23.1` from `go.mod` file

Signed-off-by: appleboy <[email protected]>

Author: appleboy

.github/workflows/go.yml

@@ -22,7 +22,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        go: [1.18, 1.19, "1.20", 1.21, 1.22, 1.23]
+        go: [1.21, 1.22, 1.23]
         include:
           - os: ubuntu-latest
             go-build: ~/.cache/go-build

go.mod

@@ -2,8 +2,6 @@ module github.com/golang-queue/redisdb-stream
 
 go 1.21
 
-toolchain go1.23.1
-
 require (
 	github.com/appleboy/com v0.2.1
 	github.com/golang-queue/queue v0.1.4-0.20221230133718-0314ef173f98