No longer support Golang 1.17.

While it might still compile with 1.17, it's no longer tested through CI
and at some point, features that require 1.18 will be used.

.github/workflows/tarball.yml

@@ -24,7 +24,6 @@ jobs:
     strategy:
       matrix:
         go-version:
-          - "1.17"
           - "1.18"
           - "1.19"
           - "1.20"
@@ -72,7 +71,6 @@ jobs:
     strategy:
       matrix:
         go-version:
-          - "1.17"
           - "1.18"
           - "1.19"
           - "1.20"

.github/workflows/test.yml

@@ -26,7 +26,6 @@ jobs:
     strategy:
       matrix:
         go-version:
-          - "1.17"
           - "1.18"
           - "1.19"
           - "1.20"

README.md

@@ -17,7 +17,7 @@ information on the API of the signaling server.
 The following tools are required for building the signaling server.
 
 - git
-- go >= 1.17
+- go >= 1.18 (usually the last three versions of go are supported)
 - make
 - protobuf-compiler >= 3