bump go.mod to Go 1.18

sashabaranov · sashabaranov · commit d0294641cedb · 2023-03-04T15:29:59.000+04:00
diff --git a/go.mod b/go.mod
@@ -1,3 +1,3 @@
 module github.com/sashabaranov/go-openai
 
-go 1.17
+go 1.18

Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,3 @@`
`1`	`1`	`module github.com/sashabaranov/go-openai`
`2`	`2`
`3`		`-go 1.17`
	`3`	`+go 1.18`