chore: update Go toolchain and Nix configuration

Taskfile.yaml

@@ -3,6 +3,8 @@ version: "3"
 
 vars:
   BIN_DIR: ./bin
+  GO_VERSION:
+    sh: sed -n 's/^go //p' go.mod
   GOLANGCI_LINT_VERSION: v2.13.2
   GOLANGCI: "{{.BIN_DIR}}/golangci-lint-{{.GOLANGCI_LINT_VERSION}}"
 
@@ -87,7 +89,6 @@ tasks:
     vars:
       IMAGE_NAME: '{{.IMAGE_NAME | default "sarin"}}'
       TAG: '{{.TAG | default "latest"}}'
-      GO_VERSION: '{{.GO_VERSION | default ""}}'
       VERSION:
         sh: git describe --tags --always
       GIT_COMMIT:
@@ -95,7 +96,7 @@ tasks:
     cmds:
       - >-
         docker build
-        {{if .GO_VERSION}}--build-arg GO_VERSION={{.GO_VERSION}}{{end}}
+        --build-arg GO_VERSION={{.GO_VERSION}}
         --build-arg VERSION={{.VERSION}}
         --build-arg GIT_COMMIT={{.GIT_COMMIT}}
         -t {{.IMAGE_NAME}}:{{.TAG}}