[go][client] fix when schema have multiple servers

[tomi77]

Fix configuration.go for schema with multiple servers (copy from go-experimental code)

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[jpriebe]

I think there is a bug in this PR. When I ran the generator, my configuration.go file had an error in it:

// NewConfiguration returns a new Configuration object
func NewConfiguration() *Configuration {
	cfg := &Configuration{
		BasePath:      "http://localhost:8080/api/v1",
		DefaultHeader: make(map[string]string),
		UserAgent:     "OpenAPI-Generator/1.0.0/go",
		Debug:         false,
		Servers:       []ServerConfiguration{{
			Url: "http://localhost:8080/api/v1",
			Description: "No description provided",
		},
			Url: "https://localhost:8080/api/v1",
			Description: "No description provided",
		},
		},
	}
	return cfg
}

(there is a missing open bracket before the second server struct literal) . The go compiler outputs this error:

./configuration.go:95:2: syntax error: unexpected }, expecting expression

[tomi77]

This bug was in previous code. This PR fix this bug.