net/http: add ShutdownGracePeriod to Server

[amyssnippet]

This change adds a new ShutdownGracePeriod field to net/http.Server to support HTTP/2 graceful shutdown as proposed in issue #77229.

Changes

• Added ShutdownGracePeriod time.Duration field to the Server struct
• Added comprehensive documentation explaining the field's purpose
• Added test TestServerShutdownGracePeriod to verify field behavior

Behavior

• Default value is 0, maintaining backward compatibility
• When > 0, HTTP/2 connections will wait this duration after sending the initial GOAWAY frame before sending the final GOAWAY
• This prevents client retries of in-flight requests during graceful shutdown

Implementation Notes

• The HTTP/2 implementation in golang.org/x/net/http2 will need to be updated to utilize this field
• No breaking changes; existing code continues to work unchanged
• Follows RFC 7540 Section 6.8 recommendations

Fixes #77229

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Message from Gopher Robot:

Patch Set 1:

(1 comment)

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Message from Amol Yadav:

Patch Set 1:

(2 comments)

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Message from Amol Yadav:

Patch Set 1:

(1 comment)

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