affected/package: xml/encoding

[larhun]

What version of Go are you using (go version)?

1.19.5

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

windows/amd64

What did you do?

After running the snippet "https://go.dev/play/p/r7BVXxvAygX" on the input data

<a xmlns="x"><b>y</b></a>

I get the output data generated by using the Encoder.EncodeToken

<a xmlns="x" xmlns="x"><b>y</b></a>

that is non-well-formed XML with a duplicated attribute name xmlns.

What did you expect to see?

<a xmlns="x"><b>y</b></a>

What did you see instead?

<a xmlns="x" xmlns="x"><b>y</b></a>

Please fix.

[seankhliao]

Duplicate of #42807