go.mod: switch to modules for dependency management

Godep is long deprecated and modules is the future.
Updating dependencies with godep is painful and non-transparent.
This will hopefully help to create custom golangci-lint linters.
The change was created with:

go mod init
rm -rf vendor
go mod vendor

Fixes #1247

5 files changed, 38 insertions, 16 deletions

diff --git a/vendor/github.com/googleapis/gax-go/v2/LICENSE b/vendor/github.com/googleapis/gax-go/v2/LICENSE
new file mode 100644
index 000000000..6d16b6578
--- /dev/null
+++ b/vendor/github.com/googleapis/gax-go/v2/LICENSE
@@ -0,0 +1,27 @@
+Copyright 2016, Google Inc.
+All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/vendor/github.com/googleapis/gax-go/v2/call_option.go b/vendor/github.com/googleapis/gax-go/v2/call_option.go
index 8b7753969..b1d53dd19 100644
--- a/vendor/github.com/googleapis/gax-go/v2/call_option.go
+++ b/vendor/github.com/googleapis/gax-go/v2/call_option.go
@@ -94,25 +94,22 @@ func (r *boRetryer) Retry(err error) (time.Duration, bool) {
 	return 0, false
 }
 
-// Backoff implements exponential backoff. The wait time between retries is a
-// random value between 0 and the "retry period" - the time between retries. The
-// retry period starts at Initial and increases by the factor of Multiplier
-// every retry, but is capped at Max.
-//
-// Note: MaxNumRetries / RPCDeadline is specifically not provided. These should
-// be built on top of Backoff.
+// Backoff implements exponential backoff.
+// The wait time between retries is a random value between 0 and the "retry envelope".
+// The envelope starts at Initial and increases by the factor of Multiplier every retry,
+// but is capped at Max.
 type Backoff struct {
-	// Initial is the initial value of the retry period, defaults to 1 second.
+	// Initial is the initial value of the retry envelope, defaults to 1 second.
 	Initial time.Duration
 
-	// Max is the maximum value of the retry period, defaults to 30 seconds.
+	// Max is the maximum value of the retry envelope, defaults to 30 seconds.
 	Max time.Duration
 
-	// Multiplier is the factor by which the retry period increases.
+	// Multiplier is the factor by which the retry envelope increases.
 	// It should be greater than 1 and defaults to 2.
 	Multiplier float64
 
-	// cur is the current retry period.
+	// cur is the current retry envelope
 	cur time.Duration
 }
 
diff --git a/vendor/github.com/googleapis/gax-go/v2/gax.go b/vendor/github.com/googleapis/gax-go/v2/gax.go
index dfc4beb28..3fd1b0b84 100644
--- a/vendor/github.com/googleapis/gax-go/v2/gax.go
+++ b/vendor/github.com/googleapis/gax-go/v2/gax.go
@@ -36,4 +36,4 @@
 package gax
 
 // Version specifies the gax-go version being used.
-const Version = "2.0.5"
+const Version = "2.0.4"
diff --git a/vendor/github.com/googleapis/gax-go/v2/go.mod b/vendor/github.com/googleapis/gax-go/v2/go.mod
index e83e87b8b..9cdfaf447 100644
--- a/vendor/github.com/googleapis/gax-go/v2/go.mod
+++ b/vendor/github.com/googleapis/gax-go/v2/go.mod
@@ -1,5 +1,3 @@
 module github.com/googleapis/gax-go/v2
 
-go 1.11
-
 require google.golang.org/grpc v1.19.0
diff --git a/vendor/github.com/googleapis/gax-go/v2/invoke.go b/vendor/github.com/googleapis/gax-go/v2/invoke.go
index 749b9d234..fe31dd004 100644
--- a/vendor/github.com/googleapis/gax-go/v2/invoke.go
+++ b/vendor/github.com/googleapis/gax-go/v2/invoke.go
@@ -38,8 +38,8 @@ import (
 // APICall is a user defined call stub.
 type APICall func(context.Context, CallSettings) error
 
-// Invoke calls the given APICall, performing retries as specified by opts, if
-// any.
+// Invoke calls the given APICall,
+// performing retries as specified by opts, if any.
 func Invoke(ctx context.Context, call APICall, opts ...CallOption) error {
 	var settings CallSettings
 	for _, opt := range opts {