Update mattermost library (#2152)

* Update mattermost library

* Fix linting

vendor/github.com/hashicorp/yamux/mux.go

@@ -0,0 +1,114 @@
+package yamux
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"time"
+)
+
+// Config is used to tune the Yamux session
+type Config struct {
+	// AcceptBacklog is used to limit how many streams may be
+	// waiting an accept.
+	AcceptBacklog int
+
+	// EnableKeepalive is used to do a period keep alive
+	// messages using a ping.
+	EnableKeepAlive bool
+
+	// KeepAliveInterval is how often to perform the keep alive
+	KeepAliveInterval time.Duration
+
+	// ConnectionWriteTimeout is meant to be a "safety valve" timeout after
+	// we which will suspect a problem with the underlying connection and
+	// close it. This is only applied to writes, where's there's generally
+	// an expectation that things will move along quickly.
+	ConnectionWriteTimeout time.Duration
+
+	// MaxStreamWindowSize is used to control the maximum
+	// window size that we allow for a stream.
+	MaxStreamWindowSize uint32
+
+	// StreamOpenTimeout is the maximum amount of time that a stream will
+	// be allowed to remain in pending state while waiting for an ack from the peer.
+	// Once the timeout is reached the session will be gracefully closed.
+	// A zero value disables the StreamOpenTimeout allowing unbounded
+	// blocking on OpenStream calls.
+	StreamOpenTimeout time.Duration
+
+	// StreamCloseTimeout is the maximum time that a stream will allowed to
+	// be in a half-closed state when `Close` is called before forcibly
+	// closing the connection. Forcibly closed connections will empty the
+	// receive buffer, drop any future packets received for that stream,
+	// and send a RST to the remote side.
+	StreamCloseTimeout time.Duration
+
+	// LogOutput is used to control the log destination. Either Logger or
+	// LogOutput can be set, not both.
+	LogOutput io.Writer
+
+	// Logger is used to pass in the logger to be used. Either Logger or
+	// LogOutput can be set, not both.
+	Logger *log.Logger
+}
+
+// DefaultConfig is used to return a default configuration
+func DefaultConfig() *Config {
+	return &Config{
+		AcceptBacklog:          256,
+		EnableKeepAlive:        true,
+		KeepAliveInterval:      30 * time.Second,
+		ConnectionWriteTimeout: 10 * time.Second,
+		MaxStreamWindowSize:    initialStreamWindow,
+		StreamCloseTimeout:     5 * time.Minute,
+		StreamOpenTimeout:      75 * time.Second,
+		LogOutput:              os.Stderr,
+	}
+}
+
+// VerifyConfig is used to verify the sanity of configuration
+func VerifyConfig(config *Config) error {
+	if config.AcceptBacklog <= 0 {
+		return fmt.Errorf("backlog must be positive")
+	}
+	if config.KeepAliveInterval == 0 {
+		return fmt.Errorf("keep-alive interval must be positive")
+	}
+	if config.MaxStreamWindowSize < initialStreamWindow {
+		return fmt.Errorf("MaxStreamWindowSize must be larger than %d", initialStreamWindow)
+	}
+	if config.LogOutput != nil && config.Logger != nil {
+		return fmt.Errorf("both Logger and LogOutput may not be set, select one")
+	} else if config.LogOutput == nil && config.Logger == nil {
+		return fmt.Errorf("one of Logger or LogOutput must be set, select one")
+	}
+	return nil
+}
+
+// Server is used to initialize a new server-side connection.
+// There must be at most one server-side connection. If a nil config is
+// provided, the DefaultConfiguration will be used.
+func Server(conn io.ReadWriteCloser, config *Config) (*Session, error) {
+	if config == nil {
+		config = DefaultConfig()
+	}
+	if err := VerifyConfig(config); err != nil {
+		return nil, err
+	}
+	return newSession(config, conn, false), nil
+}
+
+// Client is used to initialize a new client-side connection.
+// There must be at most one client-side connection.
+func Client(conn io.ReadWriteCloser, config *Config) (*Session, error) {
+	if config == nil {
+		config = DefaultConfig()
+	}
+
+	if err := VerifyConfig(config); err != nil {
+		return nil, err
+	}
+	return newSession(config, conn, true), nil
+}