Update for Go 1.15 and Vault 1.6.0

* Update to support Go 1.15 and Vault dependency levels

Update the build script to support Go 1.15.
Update the Vault API and SDK module versions.

* Update readme for levels

Author: smatzek

README.md

@@ -5,6 +5,9 @@ This plugin dynamically generates API keys for IBM Cloud service IDs. The servic
 the plugin can dynamically create it and assign it membership in a set of IBM Cloud access groups. This enables
 users to gain access to IBM Cloud resources without needing to create or manage dedicated service IDs. 
 
+## Versions
+This version of the plugin was tested with Vault 1.6.0.
+
 ## Setup
 
 1. The plugin must be built before it is installed. Follow the steps in [Developing](#Developing) to build
@@ -353,7 +356,11 @@ See docs on how to renew and revoke leases.
 ## Developing
 
 For local dev first make sure Go is properly installed, including
-setting up a [GOPATH](https://golang.org/doc/code.html#GOPATH).
+setting up a [GOPATH](https://golang.org/doc/code.html#GOPATH). The version
+of Go that is installed should match the level required by the version of Vault
+that will be used. See [Vault's requirements](https://github.com/hashicorp/vault#developing-vault)
+for more information.
+
 Next, clone this repository:
 
 ```sh

go.mod

@@ -9,8 +9,9 @@ require (
 	github.com/hashicorp/go-cleanhttp v0.5.1
 	github.com/hashicorp/go-hclog v0.14.1
 	github.com/hashicorp/go-version v1.2.1 // indirect
-	github.com/hashicorp/vault/api v1.0.4
-	github.com/hashicorp/vault/sdk v0.1.13
+	github.com/hashicorp/vault/api v1.0.5-0.20200527182800-ad90e0b39d2f
+	github.com/hashicorp/vault/sdk v0.1.14-0.20200527182800-ad90e0b39d2f
 	github.com/mitchellh/gox v1.0.1 // indirect
 	github.com/pquerna/cachecontrol v0.0.0-20200819021114-67c6ae64274f // indirect
+	google.golang.org/protobuf v1.25.0 // indirect
 )