eol_at_end_of_file    
            
            Put a single newline at end of file.
This rule is available as of Dart 2.14.0.
This rule has a quick fix available.
Details
DO put a single newline at the end of non-empty files.
BAD:
a {
}
GOOD:
b {
}
    <-- newline
Usage
To enable the eol_at_end_of_file rule,
add eol_at_end_of_file under linter > rules in your
analysis_options.yaml
file:
linter:
  rules:
    - eol_at_end_of_file