Net::HTTPHeader#connection_close?

# File tmp/rubies/ruby-3.3.0/lib/net/http/header.rb, line 966
def connection_close?
  token = /(?:\A|,)\s*close\s*(?:\z|,)/i
  @header['connection']&.grep(token) {return true}
  @header['proxy-connection']&.grep(token) {return true}
  false
end