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#STEP-1 : Add it to .gitignore file
#Step-2 : remove package-lock.json file from git track
git rm --cached package-lock.json
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# add it to the .gitignore and remove the file using the command as follow:
git rm --cached package-lock.json
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Conclusion: don't ever delete package-lock.json.
In your case you better do next way:
fix conflicts in package.json
run npm install