lint: enable some more linters

.golangci.yml

@@ -1,6 +1,10 @@
 linters:
   enable-all: false
   enable:
+    - gosimple
+    - misspell
+    - gocyclo
+    - gofmt
     - structcheck
     - varcheck
     - ineffassign

pass/cfg_test.go

@@ -12,8 +12,8 @@ import (
 
 func TestLabelTarget(t *testing.T) {
 	expect := map[avo.Label]*avo.Instruction{
-		"lblA": &avo.Instruction{Opcode: "A"},
-		"lblB": &avo.Instruction{Opcode: "B"},
+		"lblA": {Opcode: "A"},
+		"lblB": {Opcode: "B"},
 	}
 
 	f := avo.NewFunction("happypath")