Add ability to show version (and not download) when parsing version from version.tf file

[ocofaigh]

Is your feature request related to a problem? Please describe.
tfswitch --show-latest will always display the latest version. However it seems there is no way to display the version that would be installed when reading from a version.tf file without actually installing it:

% tfswitch              
Reading required version from terraform file
Reading required version from constraint: >= 1.3, < 1.4
Matched version: 1.3.9

Describe the solution you'd like
Looking for a flag to be able to output 1.3.9 from above example without actually downloading it

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

If you would like to contribute to the code, see step-by-step instructions here:

Required version

go version 1.13

Step 1 - Create workspace

Skip this step if you already have a github go workspace
Create a github workspace.

Step 2 - Set GOPATH

Skip this step if you already have a github go workspace
Export your GOPATH environment variable in your go directory.

export GOPATH=`pwd`

Step 3 - Clone repository

Git clone this repository.

git clone [email protected]:warrensbox/terraform-switcher.git

Step 4 - Get dependencies

Go get all the dependencies.

go mod download

go get -v -t -d ./...

Test the code (optional).

go vet -tests=false ./...

go test -v ./...

Step 5 - Build executable

Create a new branch.

git checkout -b feature/put-your-branch-name-here

Refactor and add new features to the code.
Go build the code.

go build -o test-tfswitch

Test the code and create a new pull request!