Default annotation not working after v0.1.8

Hello,

To begin with, thanks for your work on this package. It's great you have comment & time.Duration support !

I tried to use it as a replacement of `hashicorp/hcl` in one of my project. But based on my unit tests, `default` annotation (such as `hcl:"connection_string" default:"postgresql://user:password@localhost:5432/postgres"`) stopped working between v0.1.8 & v0.1.9.

When using `v0.1.8` of this package, tests are successful, default values are correctly set. [link to PR](https://github.com/Stoakes/go-pkg/pull/3/files) & [link to CI](https://github.com/Stoakes/go-pkg/pull/3/checks?check_run_id=2161148701)
```
github.com/Stoakes/go-pkg/config [no test files]
=== RUN Test_FileExportCommand
--- PASS: Test_FileExportCommand (0.00s)
PASS
coverage: 86.1% of statements
ok github.com/Stoakes/go-pkg/config/cmd 0.004s coverage: 86.1% of statements
```

When using v0.1.9 or higher, tests fails, default values aren't set anymore. [link to PR](https://github.com/Stoakes/go-pkg/pull/2/files) & [link to CI](https://github.com/Stoakes/go-pkg/actions/runs/673294835)

```
github.com/Stoakes/go-pkg/config [no test files]
=== RUN Test_FileExportCommand
builder_test.go:115: hcl test error. Expected "mode = false

Local {
connection_string = "***localhost:5432/postgres"
}

remote {
address = ""
useTLS = false
}
" got "Local {
}

remote {
address = ""
}
"
--- FAIL: Test_FileExportCommand (0.00s)
FAIL
coverage: 86.1% of statements
FAIL github.com/Stoakes/go-pkg/config/cmd 0.005s
FAIL
```
Tell me if I can help.