docs: specify TM version in go tutorials (#5427)

Closes https://github.com/tendermint/tendermint/issues/5425

docs/tutorials/go-built-in.md

@@ -40,14 +40,7 @@ Verify that you have the latest version of Go installed:
 
 ```bash
 $ go version
-go version go1.13.1 darwin/amd64
-```
-
-Make sure you have `$GOPATH` environment variable set:
-
-```bash
-$ echo $GOPATH
-/Users/melekes/go
+go version go1.15.1 darwin/amd64
 ```
 
 ## 1.2 Creating a new Go project
@@ -585,17 +578,37 @@ We are going to use [Go modules](https://github.com/golang/go/wiki/Modules) for
 dependency management.
 
 ```bash
+export GO111MODULE=on
 go mod init github.com/me/example
-go build
 ```
 
-This should build the binary.
+This should create a `go.mod` file. The current tutorial only works with
+tendermint > v0.34, so let's make sure we're using the latest version:
+
+```go
+module github.com/me/example
+
+go 1.15
+
+require (
+	github.com/dgraph-io/badger v1.6.2
+	github.com/tendermint/tendermint v0.34.0-rc4
+)
+```
+
+Now we can build the binary:
+
+```bash
+go build
+```
 
 To create a default configuration, nodeKey and private validator files, let's
 execute `tendermint init`. But before we do that, we will need to install
 Tendermint Core. Please refer to [the official
 guide](https://docs.tendermint.com/master/introduction/install.html). If you're
-installing from source, don't forget to checkout the latest release (`git checkout vX.Y.Z`).
+installing from source, don't forget to checkout the latest release (`git
+checkout vX.Y.Z`). Don't forget to check that the application uses the same
+major version.
 
 ```bash
 $ rm -rf /tmp/example

docs/tutorials/go.md

@@ -43,14 +43,7 @@ Verify that you have the latest version of Go installed:
 
 ```bash
 $ go version
-go version go1.14.x darwin/amd64
-```
-
-Make sure you have `$GOPATH` environment variable set:
-
-```bash
-echo $GOPATH
-/Users/melekes/go
+go version go1.15.1 darwin/amd64
 ```
 
 ## 1.2 Creating a new Go project
@@ -254,7 +247,6 @@ func (app *KVStoreApplication) BeginBlock(req abcitypes.RequestBeginBlock) abcit
 	app.currentBatch = app.db.NewTransaction(true)
 	return abcitypes.ResponseBeginBlock{}
 }
-
 ```
 
 Here we create a batch, which will store block's transactions.
@@ -444,16 +436,35 @@ dependency management.
 ```bash
 export GO111MODULE=on
 go mod init github.com/me/example
-go build
 ```
 
-This should build the binary.
+This should create a `go.mod` file. The current tutorial only works with
+tendermint > v0.34, so let's make sure we're using the latest version:
+
+```go
+module github.com/me/example
+
+go 1.15
+
+require (
+	github.com/dgraph-io/badger v1.6.2
+	github.com/tendermint/tendermint v0.34.0-rc4
+)
+```
+
+Now we can build the binary:
+
+```bash
+go build
+```
 
 To create a default configuration, nodeKey and private validator files, let's
 execute `tendermint init`. But before we do that, we will need to install
 Tendermint Core. Please refer to [the official
 guide](https://docs.tendermint.com/master/introduction/install.html). If you're
-installing from source, don't forget to checkout the latest release (`git checkout vX.Y.Z`).
+installing from source, don't forget to checkout the latest release (`git
+checkout vX.Y.Z`). Don't forget to check that the application uses the same
+major version.
 
 ```bash
 rm -rf /tmp/example