[issue] - Example "Create an Issue" Failing

## Describe the bug

The example on "Create an Issue" runs into a panic with a status code: `400`.

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## To Reproduce

Provide a link to a live example, or an unambiguous set of steps to reproduce this bug. Include configuration, logs, etc. to reproduce, if relevant.

1. Simply copy the example from the README of the repository and paste it into an editor.
2. Run the build to produce a target binary.
3. Execute the target binary and you will be presented with the error seen below.

## Expected behavior

The expected behavior should be that it creates the ticket and exits the program successfully.

## Possible Solution

Removing the `Reporter` and `Assignee` field from the `IssueFields` creates the ticket as expected but another situation occurs. Apparently dereferencing the pointers from `issue` to `i` in the print statement causes another `panic: runtime error: invalid memory address or nil pointer dereference` as seen below.

Changing `issues.Fields.Summary` to `i.Fields.Summary` gets the entire example to be working as expected.

## Your Environment

Include as many relevant details about the environment you experienced the problem in

* go-jira version (git tag or sha): de60bbe
* Go version (`go version`): go1.14.6 darwin/amd64
* Jira version: I believe it is the latest since I can't seem to get the version tag off "Inspect Element"
* Jira type (cloud or on-premise): Cloud
* Involved Jira plugins: None
* Operating System and version: Mac OS