Update Go version

[dveeden]

In go.mod we have the version set to 1.18

The Go release policy is "Each major Go release is supported until there are two newer major releases.". This means only 1.23 and 1.22 are in support.

https://go.dev/doc/devel/release#:~:text=Each%20major%20Go%20release%20is%20supported%20until%20there%20are%20two%20newer%20major%20releases.

Not sure how this would impact projects depending on go-mysql.

Not sure if there are any real benefits to bumping the version either.

If we bump the version, should we go to 1.21, 1.22? or 1.23?

diff --git a/go.mod b/go.mod
index 612dad7..d7e79cf 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/go-mysql-org/go-mysql
 
-go 1.18
+go 1.21
 
 require (
        github.com/BurntSushi/toml v1.3.2

@lance6716 @atercattus what do you think?