It was the role of his lifetime.

In the late 1980s, New York prosecutor Edward McDonald was an informal advisor on “Goodfellas.” He told director Martin Scorsese’s team about his work, in real life, with mobster Henry Hill — the protagonist in the film who is played by Ray Liotta — and helped them get all the details just right.

McDonald was even set to be a character in the film, and industry rumors suggested Brian Dennehy might play him. But McDonald quipped to Scorsese’s assistant, “What about me? I would be great!”

A week later, he found himself having a screen test in the Warner Bros. offices on 51st Street in Manhattan, in front of Scorsese himself.  

The pair got on famously and McDonald left in a daze.

When he got back to his office an hour later, there was a phone call from the movie’s screenwriter, Nick Pileggi. “Marty loved it,” he told McDonald.  “You got the part!”

Within weeks, McDonald met with Liotta and Robert De Niro.

McDonald, now 79, recounts his unlikely casting and his work prosecuting crime, in his new book “Chasing Goodfellas: Lufthansa, Henry Hill, Point Shaving, and Making Movies” (Post Hill Press, Oct. 13).

As the head of the Justice Department’s Organized Crime Strike Force in Brooklyn during the 1970s and ’80s, McDonald led complex federal investigations into the Mafia, corruption and racketeering. He secured the convictions of five corrupt US congressmen and over 70 corrupt labor officials and successfully prosecuted over 60 La Cosa Nostra members and the leaders of several Mafia families in New York. He also met Henry Hill.

A criminal since he was a kid, Hill’s rap sheet was long, including jail sentences for petit larceny, bookmaking, loan-sharking, assault and extortion. Then there were the other crimes for which he had yet to prosecuted, including robbery, bribery, truck hijackings, firearms possession and sales, burying a body and trafficking in heroin, cocaine and pills.

With so many charges hanging over him, Hill had nowhere left to turn, but rather than prosecute him, McDonald convinced him to be a cooperating witness, eventually molding him into a key government informant across a range of cases.

“Because of his affable nature and the extensive contacts he made, there were always people who would clue Henry in to promising opportunities,” writes McDonald.

Hill’s testimony proved invaluable, especially in securing convictions on the Lufthansa heist. On Dec. 11,1978, six armed men raided a Lufthansa Airlines cargo facility at John F. Kennedy airport and stole $5 million in cash and around $875,000 in jewelry (around $30 million in total today), making it the biggest robbery in US history at the time.

The heist was masterminded by Jimmy “The Gent” Burke, an associate of the Lucchese crime family — who happened to have been a mentor to Hill — along with an insider, Lufthansa employee Louis Werner.

Working with Hill, McDonald not only secured a conviction for the Lufthansa heist but also unearthed more criminality, including Burke and Hill’s 1978 scheme to corrupt Boston College basketball players by paying them to rig games.

Burke and Hill had co-opted several players in the BC team, paying them not to throw games but to manipulate the margin by which their team won or lost games, with large underground bets being made accordingly. “[Hill] explained that it was point-shaving. The kids did not have to lose,” McDonald writes. “They would get paid for games in which BC was favored, if they succeeded in keeping that margin of victory below what the oddsmakers had set as their ‘betting line’ or ‘point spread’ by which BC was favored to win.”

Ultimately, Hill’s testimony helped McDonald secure some 50 convictions across a variety of cases. In turn, McDonald ensured that Hill, his wife and his two children entered the Witness Protection Program. As for himself, the lawyer was never that worried about his own safety.

“I was never seriously concerned about violence or threats from the mob,” he said. “I believed that the bosses had sent out the message that any harm or threats to prosecutors would result in far too much heat and no one should ever be so stupid. 

“Perhaps we were naïve or wishfully thinking.”

When “Goodfellas” was released in September 1990, it met with critical and commercial acclaim, receiving six Oscar nominations and winning one, Best Supporting Actor, for Joe Pesci’s portrayal of psychotic mobster Tommy DeVito.

McDonald’s performance was also singled out. “People are going to remember you for this movie!” screenwriter Pileggi told him. “Plus, you’re the only actor who doesn’t curse — a lot.”

In the book, McDonald writes of how working with Hill not only resulted in a movie role but also gave way to a decades-long friendship.

“There was something about Henry that made him likeable. He was charming, self-deprecating, and funny,” he writes. “We could never forget how despicable and sometimes infuriating he could be, but he was often fun to be around.”

Hill died from smoking-related heart issues at West Hills Hospital in West Hills, Los Angeles, on June 11, 2012, the day after his 69th birthday. 

“It was amazing he lived so long,” McDonald said. But, “as Henry said in ‘Goodfellas,’ ‘it was a glorious time.’ ”