Revert "bump go verseion to 1.21 and use new builtin functions (#1155)" (#1179)

Ignite currently does not support go 1.21. So reverting this change
until the support is added.

This reverts commit 8981fd6.

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---------

Co-authored-by: Ganesha Upadhyaya <gupadhyaya@Ganeshas-MacBook-Pro-2.local>
Co-authored-by: nashqueue <99758629+nashqueue@users.noreply.github.com>

Author: 3 people

.github/workflows/ci_release.yml

@@ -27,12 +27,12 @@ jobs:
   lint:
     uses: ./.github/workflows/lint.yml
     with:
-      GO_VERSION: "1.21"
+      GO_VERSION: "1.20"
 
   test:
     uses: ./.github/workflows/test.yml
     with:
-      GO_VERSION: "1.21"
+      GO_VERSION: "1.20"
 
   proto:
     uses: ./.github/workflows/proto.yml

README.md

@@ -10,7 +10,7 @@ A modular framework for rollups, with an ABCI-compatible client interface. For m
 
 ## Building From Source
 
-Requires Go version >= 1.21.
+Requires Go version >= 1.20.
 
 To build:
 

go.mod

@@ -1,6 +1,6 @@
 module github.com/rollkit/rollkit
 
-go 1.21
+go 1.20
 
 require (
 	github.com/celestiaorg/go-header v0.2.13